# Numericals based on concave/convex lens and power

Numericals based on concave/convex lens and power
CLASS-X
LIGHT
ASSIGNMENT-3
Q1. A 4cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20cm. If the distance of the object is 30cm from the lens, find the position, nature and size of the image. Also find its magnification.
Ans: v=60cm, hi= -8cm, inverted, m= -2
Q2. A needle placed at 45cm from the lens forms an image on a screen placed 90cm on the other side of the lens. Identify the type of the lens and determine its focal length.
Ans: f= +30cm, convex lens
Q3. An object 2cm high is placed at a distance of 64cm from a white screen. On placing a convex lens at a distance of 32cm from the object it is found that a distinct image of the object is formed on the screen. What is the focal length of the convex lens and size of the formed on the screen?
Ans: f= 16cm, hi= -2cm (same size, inverted)
Q4. A 10cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30cm. The distance of the object from the lens is 20cm. Find the position, nature and size of the image formed.
Ans: v= -60cm, hi= +30cm, erect
Q5. One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Q6. A concave lens of focal length 20cm forms an image at a distance of 10cm from the lens. What is the distance of the object from the lens?
Ans: u= -20cm
Q7. Find the position and nature of image formed when an object is placed at a distance of 5cm from a concave lens of focal length 15cm. What is its magnification?
Ans: v= -3.75cm, virtual and erect, m= 0.75
Q8. An object located 32cm in front of a lens forms an image on a screen 8cm behind the lens.
a) Find the focal length of the lens.
b) Determine its magnification.
c) Is the lens converging or diverging?
Ans: f= 6.4cm, m= -1/4,…

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